1989: Tim Berners Lee proposed using the hypertext foraccessing the information of the computers at CERN

4

Web History

Web

Protocols

and

Practice

INTRODUCTION

During1980-1990these systems have been used widelyon Internet to access the information :

FTTP: For file transfer. It works by knowing the ftp server.

Gopher: Provided the ways for the users to search theservers in the network.

WAIS (Wide Area Information Servers): Allowed users tosend queries to the databases around the network.

Archie: Global index of ftp servers that allowed the users todo the search based on file name.

1992: The first official release of the web browser.

1993: First graphical web browser (MOSAIC)

5

Web Definition

Web

Protocols

and

Practice

INTRODUCTION

The World Wide Web, or simply the Web, is theuniverse of information accessible via networkedcomputers.

Internet is different from web. It is a network ofcomputers, in which a computer may notnecessarily act as a web client or web server.

6

Semantic Components of the Web

Web

Protocols

and

Practice

INTRODUCTION

Three main semantic components of the Webare:

A naming infrastructure (URI)

A document language (HTML)

A message exchange protocol (HTTP)

7

URI (Uniform Resource Identifier)

Web

Protocols

and

Practice

INTRODUCTION

Accessing and manipulating resources distributedthroughout the Web requires a way to identify them. URIis a universal naming mechanism for identifying resourceon Web independent of its current location or value.

URI can be thought of as a pointer to a black box towhich request method can be applied to generatedifferent responses at different times. Request method isa simple operation such as fetching, changing, ordeleting a resource.

High user perceived latency can be because ofvariety of factors such as:

DNS overhead

Network congestion

Load on server

Analysis of logs is a useful for knowing theworkload characteristics such as time betweenthe requests and size of the requests andresource popularity, which have the importantimplications on Web performance

26

Table 1.6.Terminology related to Web traffic and performance

Definition

Term

Time between the initiation of an action and the first

Indication of a response

Time between a user action and the initial display of

the content

Amount of traffic that can be carried per unit time

Inputs received by a Web component over time

Record of transactions performed by a Web

component

Latency

User-perceived

latency

Bandwidth

Workload

Log

Web

Protocols

and

Practice

INTRODUCTION

27

Web Applications

Web

Protocols

and

Practice

INTRODUCTION

Important applications are:

Web caching

»Caching moves contents closer to the user.

»A cache can be located at



A user's browser



An origin server



A machine in the path between the user and theorigin server

Multimedia streaming

»The client plays the samples and frames as theyarrive from the server, rather than downloading thecontent in its entirety before beginning playout.